1. Adams, R.A., Fournier, J.F.: Sobolev spaces. Academic Press, New York (2003)
2. Adams, Robert A.: Sobolev spaces. Academic Press [A subsidiary of Harcourt Brace Jovanovich, Publishers], New York-London, 1975. Pure and Applied Mathematics, Vol. 65
3. Andrews, George E., Askey, Richard, Roy, Ranjan: Special functions. Encyclopedia of Mathematics and its Applications, vol. 71. Cambridge University Press, Cambridge (1999)
4. Askey, Richard.: Orthogonal polynomials and special functions. SIAM, Philadelphia, Pa., 1975
5. Babuška, Ivo., Guo, Benqi.: Direct and inverse approximation theorems for the $$p$$-version of the finite element method in the framework of weighted Besov spaces. I. Approximability of functions in the weighted Besov spaces. SIAM J. Numer. Anal., 39(5):1512–1538, 2001/02